A watermark used for an information security is a technique for inserting a mark, which is known to only an owner, to an original content, such as a text, an image, a video, an audio, and the like, so that the content cannot be identified by human naked eyes or ears. When ordinary users illegally copy digital information and use it for a commercial or other usage without proper payment or permission, the owner of the content can disclose that the content belongs to the owner by extracting the watermark of the owner.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.